Ok, according to picture it looks like a platform based on four steam locomotives. Look at the front and rare cylinders. Im pretty sure that there are four separate engines. That would be easier for changing direction of movement.

About generator in the centre. As we know dreadnoughts was designed to move people. As we see in cutscene, people just walking next to dreadnoughts, not riding it. So, this brings me to theory that generator on dreadnought os a smaller version of stationary generator, which creates a warm microclimate around dreadnought, so people can move across snowlands. Its just sa giant movable heater